Clothes dryer control apparatus



June 5, 1962 K. D. COOLEY ETAL CLOTHES DRYER CONTROL APPARATUS 2 Sheets-Sheet 1 Filed NOV. 4, 1957 BMEEI ME Mme/Sm wm amt/mo immv E M 0 DE N T RN NA 0 mc n T W QZM HD TLL EOE RT MAS K Y B June 5, 1962 COOLEY ETAL3,037,296

CLOTHES DRYER CONTROL APPARATUS KENNETH D. COOLEY HAROLD F. SNIDER BYESTEL c. KANEY United States Patent 3,037,296 CLOTHES DRYER CONTROLAPPARATUS Kenneth D. Cooley, Harold F. Snider, and Estel C. Raney, FortLauderdale, Fla., assignors to Ranco Incorporated, Columbus, Ohio, acorporation of Ohio Filed Nov. 4, 1957, Ser. No. 694,374 9 Claims. (CI.34-45) The present invention relates to control apparatus for clothesdryers, particularly of the domestic type comprising a rotatable clothesdrum, an air heater, a blower for forcing the heated air through thedrum, and a motor for driving the blower and drum.

It is well known that during the clothes drying cycles of the type ofdryer mentioned, with a relatively heavy or wet load of clothes, thetemperature of the discharged drying air initially rises rapidly until acertain degree is reached after which the rate of rise levels off orfalls to an insignificant rate, due to evaporation of moisture from theclothes, and when the clothes become nearly dried the temperaturecommences to rise again relatively rapidly. Accordingly, one object ofthe present invention is to provide an improved automatic control for aclothes dryer in which drying cycles may be terminated by meansresponsive to a relatively rapid rise in temperature of the dischargeddrying air.

As mentioned, during the initial warm-up of the drying air, thetemperature rise is relatively rapid, and to prevent prematuretermination of the drying cycle by the means responsive to therelatively high rate of temperature rise, it is a further object of theinvention to provide means to maintain the drying cycle irrespective ofthe operation of the means responsive to the rate of temperature risefor a period to permit the drying air to attain the temperature at whichit would normally attain a low rate of rise due to evaporation ofmoisture from the clothes.

The length of time that the discharged air temperature remainssubstantially constant or rises at a relatively slow rate variesaccording to the amount of moisture in the clothes which may depend uponthe fabric and amount of the clothes in the load. Thus, when there is anappreciable amount of water present, the rate of temperature rise of thedischarged air will change from a relatively low to a relatively highrate causing the improved control to terminate the drying cycle. Whenthe moisture content is low,

however, the rate of temperature increase may be relatively highthroughout the drying cycle which would nullify the effectiveness of therate rise responsive means. Therefore, a still further object of theinvention is to provide control means to initiate, maintain andterminate a minimum drying cycle, which means becomes subjected to thecontrol of the temperature rate responsive means during the drying cycleso that in the event substantial moisture evaporation is taking place,the operation of the cycle control means will be interrupted to permitcontinuation of the drying cycle until the rate of temperature increaseof the discharge air becomes relatively high, indicating a dry conditionof the clothes; otherwise, the cycle control means continues its minimumdrying cycle control.

A still further object of the invention is the provision of a rate oftemperature rise responsive means comprising two thermally responsiveelements arranged to be sub jected to air exhausted from the clothesdrum, one element being modified to cause it to lag in its movementrelative to the other in response to relatively rapid changes intemperature and both elements actuating a control device, such as aswitch, to one position when both elements are subjected to relativelyeven or slow changing temperatures and to move the control device to asecond control position when the exhaust air temperature risesrelatively rapidly so as to cause the lagging element to move lessresilient contact arm 28.

3,037,296 Patented June 5, 1 962 than the other element. The rapid risein temperature indicates a decreased moisture absorbing condition, whilea relatively slow temperature rise, below a maximum, indicates arelatively heavy moisture absorption of the drying air.

Still a further object of the invention is to cycle the operation of theair heater between maximum and minimum limits so that should thetemperature of the exhaust air gradually increase, as may be the casewith some types of cloth, the maximum temperature will be limited to asafe degree and the temperature increasing phases of these cyclesprovide temperature increasing phases on which the rate of temperatureincrease sensing responsive may be readily eilected.

=Further objects and advantages of the invention will be apparent fromthe following description of a preferred embodiment, reference being hadto the accompanying drawings wherein:

FIG. 1 is a schematic showing of a control apparatus embodying theinvention in a clothes dryer; and

FIGS. 2, 3 and 4 are charts indicating changes in temperatures of theshielded and unshielded thermostatic power elements during drying cyclesof a light load of clothes, a normal load of clothes and a relativelyheavy load of clothes, respectively.

Referring to FIG; 1 of the drawings, the invention is shown in a controlapparatus for a conventional electrical heater type clothes dryer, andfor sake of clarity only the portions thereof essential to theunderstanding of the invention are illustrated. It will be understood bythose familiar with the art thatthe control apparatus could also controla solenoid valve of a gas burner type clothes dryer instead of theelectric heater type disclosed. The control apparatus comprises a timerdevice 10 including a synchronous motor arrangedto drive a shaft 11through suitable gearing, not shown, at the rate of about one revolutioneach twelve minutes, and the shaft has switch actuating cams 13-, 14,attached thereon. Shaft 11 is preferably driven through a slip clutch(not shown) to permit manual rotation thereof by a knob 16 attached tothe outer end thereof to initiate operation of the dryer and tosupersede automatic control, if desired.

Cam 13 opertates electric switches 18 and 19, switch 18 comprising aspring arm 20 having a finger 21 which rides the cam periphery, and acontact 22 which engages a double contact 23 when arm 20 is flexedupwardly by the cam. Contact 23 is attached to the free end of aflexible contact arm 24 which may be flexed upwardly by arm 29 to engagecontact 23 with a contact 27 carried on a As is explained hereinafterswitch 18 controls the circuit of the clothes drum and blower motor andswitch 19 controls the air heater circuit and carn 13 may close bothswitches at once or only switch 18. 9

Cam 13 has a dwell 30 which causes contact arm 20 to drop the positionshown in FIG. 1 to open switches 18, 19 to de-energize the dryer.Adjacent the dwell 30 is a rise 31 which, when the cam 13 is rotatedclockwise as viewed in the drawing, causes contact arm 20 to be tlexedupwardly and engage contacts 22, 23, 27 to close both the motor andheater circuits. Preferably, a notch 32 is formed in the periphery ofcam 13 to providea detent to indicate to the operator that the cam hasbeen set in the starting position. Cam 13 has a drop 33 arranged tocause contact arm 20 to drop and separate contact 23 from contact 27 toopen the heater circuit switch 19 while maintainin contact 22 inengagement with contact 23. A second drop 34 on cam 13 is arranged tocause contact arm 20 to drop into dwell 30 and separate contacts 22, 23to open the motor switch'18.

Step 33 is positioned from notch 32 such that switch 19 will be openedapproximately nine minutes after timer is energized, and step 34 ispositioned relative to step 33 so that the motor switch 18 will beopened approximately three minutes after opening of the heater switch19.

Cam 14 operates a switch 36 comprising a spring contact arm 37 carryinga contact 38 which is arranged to engage a fixed contact 39 supported ona terminal 40. Contact arm 37 has a finger 41 which rides on cam 14, andthe cam is shaped to maintain contacts 38, 39, in engagement exceptmomentarily when finger 41 drops into a notch 42 which is positioned toregister with finger 41 approximately eight minutes after initiation ofoperation of timer 10.

The construction of the timer device 10 including the switches operatedby the cams is like that well known in the art and the details thereofare therefore not more fully shown.

In the form of the invention shown, the means responsive to the rate ofmoisture removal comprises two similar thermally responsive powerelements 43, 44. Element 43 comprises a rigid cylindrical body 45 havinga plunger 46 which moves axially in and out of the end thereof inaccordance with changes in volume of a liquid contained in a tube 47 andbulb 48 connected with the interior of the body. The construction ofthermal element 43 is like that shown in the patent application ofFrederick A. Greenawalt, Serial Number 345,065, filed March 27, 1953,although it is to be understood that any other suitable thermallyresponsive element may be utilized in the practice of the invention.

The thermally responsive element 44 is like the element 43 except thebulb 49 thereof has a coating of insulating material 50 thereon toreduce the rate of heat exchange between the liquid within the bulb andthe air surrounding the bulb. Bulbs 48, 49 are both placed in theexhaust air duct 51 of the dryer, only a portion of which appears in thedrawings, so that the two bulbs are subjected to the temperature of theair as it is discharged from the clothes drying drum of the dryer.

An L-shaped lever 53 is pivoted at 54 to the plunger 46 of thermallyresponsive element 43 and the left hand end thereof is engaged by theplunger 55 of element 44. Lever 53 is urged downwardly by a tensionspring 56 connected thereto as shown.

Vertical movement of plunger 46 of thermal element 43 is arranged toopen and close a toggle switch comprising a contact arm 57 pivoted atits right hand end and which has a contact 58 arranged to engage a fixedcontact 59 during the time the temperature of the bulb 48 is below acertain maximum which may be 180 F, for example. Contact arm 58 isconnected to lever 53 through a toggle spring 60 which is insulated fromlever 53 and which snaps contact arm 57 upwardly to a stop 61 when thetemperature of bulb 48 reaches approximately 180 F. and snaps the armback to contact 59 when the temperature of bulb 48 falls to 140 F. Anysuitable switch could be used which will open and close by movement ofplunger 46 corresponding to exhaust air temperatures of approximately180 F. and 140 F., respectively, and the construction shown is more orless schematic.

The depending leg 53' of lever 53 is arranged to move a contact member62 to the right and engage a contact 63 carried thereby with a fixedcontact 64 and this will occur when the movement of plunger 46 exceedsmovement of plunger 55 by a predetermined amount as is more fullyexplained hereinafter.

The electrical heating element of the dryer is shown at 66 and it isarranged to heat air which is then directed through the clothes drum(not shown) in a conventional manner, and the circuit for element 66includes power line L1 of a conventional 230 v. three-wire system,switch 19, wire 67, contacts 59, 58, contact arm 57, wire 68 to one sideof heater 66 and the opposite side of the heater is connected to L2 ofthe power circuit. In conventional constructions it is desirable toplace a switch in the L2 side of the circuit for heater 66 so that bothsides of the heater may be broken when the dryer is de-energized, butfor the sake of clarity this switch has been omitted.

The fan and clothes drum of the dryer are driven by an electric motor 70and the circuit for this motor includes line L1, switch 18, wires 71, 72to one side of the motor, and wire 73 to N of the power circuit.

The circuit for the synchronous motor of the timer device 10 comprises Nof the power lines, which is attached to one terminal thereof, and theother terminal is connected by wire 75 to switch 36, wires 74, 71,switch 18 to L1. An alternate circuit to L1 around switch 36 may beestablished for the timer motor through wire 75 to contacts 64, 63,contact arm 62, wires 72, 71 and switch 18.

The operation of the control apparatus is as follows:

Assuming that a relatively light load of clothing is placed in the drumof the dryer, such as one-quarter of a pound, the operator turns theknob 16 clockwise, as viewed in the drawings, to the on position whichrotates cams 13, 14 to close switches 18, 19, 36 which energize theblower motor 70, heater element 66 and the motor of the timer device 10,through the circuits described previously. It has been found that with alight load of clothing, or clothing having a relatively low watercontent, the discharge air temperature will maintain a more or lesssteady and relatively rapid rise until a dry condition is reached, whichtemperature rise is illustrated by the full line in the graph shownin-FIG. 2, and the clothes will become dried within a relatively shortperiod, such as from 6 to 8 minutes as a minimum, depending on the thedegree of heat applied to the air. The insulation 50 on bulb 49 preventsthe thermal element 44 from responding at the same rate as does thermalelement 43 and therefore plunger 55 lags in movement relative to themovement of plunger 46 and under these conditions contacts 63 and 64will be closed by lever 53 shortly after commencement of operation ofthe dryer and will be maintained closed until after switch 36 has beenopened and reclosed by cam 13. The broken line in the graph of FIG. 2illustrates the temperature rise of the liquid in bulb 49 as compared tothe exhaust air temperature. It will be noted that in the event the loadis so light that the exhaust air temperature reaches 180 F., powerelement 43 will open contacts 59, 60 to de-energize the heater and willreclose the contacts when the air temperature falls to F. The lag inresponse of element 44 causes contacts 63, 64 to be closed on eachheating cycle. At the end of approximately 8 minutes the notch 42 of cam13 moves into registration with finger 41 and arm 37 drops to openswitch 36. The opening of switch 36 would break the timer circuit exceptfor the fact that the alternate circuit for the timer is now closedthrough contacts 63, 64, at least during the rise in discharge airtemperature, and the timer therefore continues to operate and reclosesswitch 36 to re-establish the timer circuit through the latter. Afteranother minute of operation, the timer opens the heater circuit atswitch 19 and after three more minutes of operation cam 13 opens switch18 to de-energize the blower motor and the timer motor. It will be seenthat since the rate of moisture removal was not sutficient to cause aleveling of the rate of rise of discharge air temperature, the dryer wasoperated for a minimum drying time as determined by the timer device.

Should a heavier and more moisture laden load of clothes be placed inthe dryer and the drying cycle started as described relative to thelighter load, the temperature at bulb 48 will rise as indicated by thefull line in FIG. 3 until a leveling oif occurs which indicates that theheated air is absorbing considerable moisture from the clothes, and thetemperature of the liquid in insulated bulb 49, which is represented bythe broken line, will shortly thereafter rise to the same temperature asthat of the liquid in bulb 48. This is indicated at point a on the graphand at this time contact 63 will be separted from contact 64 as shown inFIG. 1. Assuming that the amount of moisture present in the clothes issufficient to bring about the temperature plateau eflect, which openscontacts 63, 64 as described, within eight minutes after initiation ofthe dryer cycle, finger 41 drops into notch 42 of cam 14 and causesswitch 36 to open and break the timer circuit, which tie-energizes thetimer to interrupt its timer cycle. Switches 18, 19 will then bemaintained closed to continue the drying cycle until such time as themoisture content of the clothes materially decreases'which results inthe discharge air temperature rising relatively rapidly, as indicated atthe point b in FIG. 3, and bulb 48 will correspondingly increase intemperature and cause plunger 46 to move upwardly more rapidly thanplunger 55 to thereby tilt lever 53 counterclockwise and close contacts63, 64 to re-energize the timer circuit. The reoperation of the timercloses switch 66 to maintain the timer circuit independently of theposition of contacts 63, 64 and opens switches '19, and 18 in thesequence described to terminate the heating cycle and then the blowermotor operation, as described previously. It will be noted that duringthe first eight minutes of operation under the load conditionsmentioned, contacts 63, 64 may or may not be closed depending upon theheater capacity or the temperature of the dryer mechanism at the startof the drying cycle, etc., but this action has no effect on the timerwhich is maintained energized through switch 36 for the first eightminutes.

It has been found that with exceedingly heavy wet load the temperatureof the exhaust air is apt to gradually increase until it reaches arelatively high degree, such as 180 F. This condition is illustrated bythe heavy line in FIG. 4. When the temperature of the exhaust airreaches 180 F. the plunger 46 of the thermally responsive element 43 isextended to the point where it elevates the lever 53 to a position inwhich spring 60 snaps contact arm 57 upwardly to separate contacts 58,59 to there by break the circuit of heater 66. As explained previ ously,the contact arm 57 is held upwardly until the plunger 46 has receded ordescended to a position corresponding to 140 F. in the discharged airtemperature at which time contacts 58 close on 59 and re-establish theheater circuit. This is illustrated at point d on the drawing and uponre-energization of the heater element the temperature of the aircommences to increase once more and if a substantial or an appreciableamount of moisture is still being removed from the load the rate of riseof temperature of bulb 48 is approximately the same as that of theshielded bulb 49 so that contacts 63, 64 will not be closed and thetimer will remain de-energized. This cycling of the heater element maycontinue until such time as the heating cycle rises at a rate which isso much faster than the rate of rise of the insulated or shielded bulb49 that the lever 53 is tilted to close contacts 63, 64 which againre-energizes the timer motor causing cam 14 to reclose switch 36 andmaintain the circuit of the timer motor in the alternate circuit aroundcontacts 63, 64. The drying cycle is then terminated in the mannerdescribed previously, that is to say, cam 13 first opens switch 19 tode-energize the heater and after approximately three minutes switch 18is opened to de-energize the blower motor and timer motor.

It will be seen that by limiting the temperature of the discharge air asdescribed, repeated samplings of the rate of temperature increase can betaken according to the relative rates of temperature changes in thebulbs 48, 49.

An important advantage of the improved control system is that theoperator of the clothes dryer need not be concerned with adjustments ofthe control apparatus to compensate for the weight of the clothes, thedegree of moisture therein or ambient temperature or humidity to securethe proper degree of drying, and once set, the control apparatusmaintains automatically the most eflicient and economical control of thedrying cycle.

While but one form of the invention has been disclosed it is to beunderstood that other forms, modifications and adaptations could be madeall falling within the scope of the claims which are attached hereto. Itis to be understood that the dryer apparatus referred to in the claimsis not necessarily limited to clothes dryers but includes dryingapparatus for other materials.

We claim:

1. A control system for drying apparatus utilizing heated air as adrying medium and comprising: control means operative to initiate,maintain and terminate a drying cycle; means including a control devicemovable between first and second control positions in response,respectively, to relatively rapid and relatively slow rates oftemperature increases of air discharged from the clothes to be dried;and means operative during said drying cycle to establish cooperativerelation between said control means and said control device so that inthe event said control device is in said first control position theoperation of said control means is continued and operative when saidcontrol device is in said second control position to interrupt operationof said control means to prolong said drying cycle until said controldevice shifts to said first control position to effect continuation ofoperation of said control means to complete the drying cycle.

2. A control system for drying apparatus utilizing heated air as adrying medium and comprising: control means operative to initiate,maintain and terminate a drying cycle; two thermally responsive elementsresponsive to the temperature of the discharged drying air and havingdifferent rates of response, a control device movable between first andsecond control positions by relative responses of said thermal elementsin response, respectively, to a relatively rapid and a relatively slowrate of temperature increase of air discharged from the clothes to bedried; and means operative during said drying cycle to subject theoperation of said control means to said control device so that shouldsaid control device he in said first control position the operation ofsaid control means is continued and in the event said control device isin said second control position, the operation of said control means isinterrupted to prolong said drying cycle until after said control deviceshifts to said first control position to efiect continuation ofoperation of said control means to complete the drying cycle.

3. A control sysem for a clothes dryer having an air heater, a clothescontainer and means for passing air over the heater and through thecontainer, said control system comprising an electric powered timerdevice for controlling the heater, said device being manually settableto render said heater effective and operative to subsequently rendersaid heater ineffective after a predetermined timing movement, a circuitfor said timer device including parallel branches, one branch includinga first control switch and the other branch a second control switch, twothermally responsive elements responsive at difierent rates to increasesin temperature of air discharged from over the clothes and operating toclose said first switch by differential in response to a relativelyrapid rate of temperature rise of the discharged air and to open saidswitch in response to a relatively low rate of increase in thedischarged air temperature, and means to momentarily open said secondswitch after a predetermined period of operation of said timer devicewhereby the circuit to said timer is broken after a predetermined periodof operation of said timer when the rate of temperature rise isrelatively low and the timer circuit is closed to continue operation ofthe timer when the rate of temperature rise of the discharged air isrelatively high.

4. A control system as defined in claim 1 and having means, subject tothe operation of said control means, to reduce the temperature of saidair in response to a predetermined maximum temperature of the dischargeair and to then increase the temperature of said air in response to thereduction in discharge air temperature to a lower temperature, wherebythe temperature of the discharged air is alternately lowered and raisedfrom and toward a relatively high temperature limit after attaining apredetermined high temperature.

5. In a drying apparatus having electrically energized means to passheated air into contact with material to be dried to provide a dryingcycle and including an air heater and a blower, control mechanism forinitiating and automatically terminating operation of said heater andblower and comprising: a circuit including a first switch to controlsaid heater; electrically operated timer means to open said switch aftera predetermined period of operation thereof; circuit means to energizesaid electric timer means, including a main circuit and two parallelcircuits connected in series with said main circuit, said main and twoparallel circuits including second, third and fourth switches,respectively; manually settable means to close said second switch;sensing means responsive to the temperature of the drying air dischargedfrom the material to be dried and operable in response to an increase inrate of temperature rise above a given rate of temperature rise to movesaid fourth switch from an open to a closed position; and means tomaintain said third switch normally closed and to open and reclose thelast mentioned switch during said predetermined period of operation ofsaid timer means.

6. Control mechanism in a drying apparatus as defined in claim includingmeans to cause the temperature of the air discharged from the materialto be dried to fluctuate between a predetermined high limit and amaterially lower temperature.

7. In a drying apparatus having means to pass heated air into contactwith material to be dried to provide a drying cycle, control mechanismfor initiating and automatically terminating the supply of heated air bysaid means and comprising: settable means to operate the first mentionedmeans for initiating a drying cycle; timer means to terminate saidsupply of air after a predetermined period of operation thereof; meansto initiate operation of said timer means; and alternative means tocontrol operation of said timer means, one of said alternative meansbeing responsive to the temperature of the drying air discharged fromthe material to be dried and operable in response to an increase in rateof temperature rise above a given rate of temperature rise to rendersaid timer operative, and said other alternative means being operable tomaintain operation of said timer means during an initial portion of saidpredetermined period of operation of said timer means.

8. In a drying apparatus and control mechanism there for as set forth inclaim 7 characterized by said other alternative means being operableafter said initial portion of said predetermined period to conditionsaid timer means to discontinue operation and subject to the control ofsaid one alternative means.

9. In a drying apparatus having means comprising a blower and a heaterto pass heated air into contact with material to be dried to provide adrying cycle, control mechanism for initiating and automaticallyterminating operation of said heater and comprising: means to initiateoperation of the first mentioned means to establish a drying cycle;means to terminate operation of said heater of air including sensingmeans responsive to the temperature of the drying air discharged fromthe material to be dried and operable in response to an increase in rateof temperature rise above a given rate of temperature rise to effecttermination of operation of said heater; and means to maintain operationof said heater and blower during a substantial period followinginitiation of the drying cycle by said second mentioned means,irrespective of the operation of said sensing means whereby the responseof said sensing means to the rapid rise in dis charge air temperaturenormally occurring during the period immediately following initiation ofa drying cycle is ineffective to terminate the drying cycle.

References Cited in the file of this patent UNITED STATES PATENTS1,567,710 Carroll Dec. 29, 1925 1,846,752 Picard et a1 Feb. 23, 19322,654,961 Manecke Oct. 13, 1953 2,717,455 Harris et al. Sept. 13, 19552,743,531 Steward May 1, 1956 2,744,337 Raney May 8, 1956 2,769,246Shapter Nov. 6, 1956 2,775,047 Morrison Dec. 25, 1956 2,820,304 HoreckyJan. 21, 1958 2,825,146 Kostelich Mar. 4, 1958 2,851,789 Dunkelman Sept.16, 1958 2,878,579 Fuchs Mar. 24, 1959 2,895,230 Reiley Apr. 20, 1959

